Fuel injection system



June 16, 1959 I c. D. ST'RANG 2,390,692

' FUEL INJECTION SYSTEM v 4 Filed Ju}y 1, 1957 INkENTOR. CHARLES Q. STRANG BY United taes FUEL INJECTION SYSTEM Charles D. Strang, Oshkosh, Wis., assignor to Kiekhaefer Corporation, Cedarburg, Wis., a corporation of Wisconsin Application July 1, 1957, Serial N 0. 669,247

'7 Claims. (Cl. 123-140) This invention relates to fuel injection systems and more particularly to a system which utilizes a combination of injection and carburetor systems.

In the conventional fuel injection system there is usually provided an injection valve in the cylinder head, an injection pump for supplying variable amounts of fuel to the injection valve, and a throttle valve for supplying air to the engine and which regulates a diaphragm of the pump to vary the amount of fuel delivered thereby.

When such an injection system is used in small engines, for example in a two-cycle outboard motor for a boat, difficulties have been encountered in accurately metering extremely small quantities of fuel for idle conditions.

It is therefore an object of this invention to provide a fuel supply system which utilizes the injection principle at operating conditions other than idle, and utilizes a carburetor supply system at idle conditions. The combination system provides that a common throttle valve acts to cause the injection system to become inoperative when the idle condition is desired at which time the carburetor becomes operative. Conversely, when the throttle is moved from idle to higher speed positions, the

injection system is brought into operation and the carburetor action ceases.

Another more specific object of the invention is to provide a combination injection and carburetor fuel supply system having a throttle body that acts as a carburetor at idle speeds and acts as a fuel injection pump control device at other speeds.

Other objects and advantages of the invention will appear hereinafter as this disclosure progresses, reference being had to the accompanying drawings, in which:

Figure 1 is a schematic diagram, showing parts in section, of a fuel supply system utilizing the invention; and

Figure 2 is a schematic cross-sectional view, on an enlarged scale of the throttle mechanism shown in Figure 1.

Referring more particularly to the drawings, a two cycle engine 10 is shown which has a fuel supply tank 11, fuel injection pump 12, fuel feed pump 13, and fuel filter 14. The throttle body 16 has a mixing chamber 17 and is in air delivering communication with the engine cylinders via the crankcase and passage 15. A throttle valve in the form of a butterfly valve 18 is pivotally mounted in chamber 17 and is manually operable by the lever 19. The throttle body also includes a Venturi section 20 located just ahead of the throttle valve.

The injection pump 12 is of conventional design and includes the pump housing 21 from which extends thedelivery pipe 22, vent pipe 23 and inlet pipe 24. A diaphragm housing 25 and diaphragm 26 define a vacuum chamber 27 through which extends the control rod 28 which is secured to diaphragm 26 for movement thereby.

A vacuum conduit 29 connects the vacuum chamber 27 and the mixing chamber 17, terminating in the latter adjacent the butterfly valve.

When the engine is operating at other than idle speeds,

Patented June 16, 1959 the delivery of the injection pump is adjusted in accordance with the vacuum formed in the air intake pipe of the running engine, which in turn is dependent on speed and load. The butterfly valve acts as a throttle and a vacuum is created behind the valve which increases with an increase in engine speed. Also, the more the valve constricts the area of passage, the higher the vacuum becomes. The Venturi shape of the passage contributes to increasing the vacuum formed.

The vacuum is propagated through conduit 29 into the chamber 27 of the diaphragm unit. A governing spring 31 in the vacuum chamber loads the diaphragm and the control rod in the direction of full load (to the left in the drawings), While the vacuum in the chamber 27 (more particularly the atmospheric pressure on the opposite side of the diaphragm) urges the control rod in the direction of stop, that is, to the right. 1

In operation, if the engine speed tends to increase without the position of the butterfly valve having been altered, the absolute pressure at the vacuum chamber drops and the diaphragm and control rod are displaced in the direction of stop. Less fuel is beingvinjected in conformity with the reduced air filling, and the engine slows down. As a result, the absolute pressure at the vacuum chamber immediately increases again owing to the increased air filling, and the control rod is displaced in the direction of full load. A certain equilibrium is thus quickly established. I

When the butterfly valve is manually moved, as by depressing a foot pedal (not shown) when more speed is desired, the absolute pressure at the vacuum end increases. The control rod is moved to the left to increase the fuel being injected and the engine accelerates to the speed corresponding to the position of the butterfly valve. If the foot pedal is released, the pressure at the vacuum end drops and the engine slows down to the speed at which equilibrium again prevails.

The system has all the advantages of a fuel injection system. However, from apractical standpoint, it has been found very difficult to accurately meter very small quantities of fuel with a fuel supply system of the above type. This has been particularly true in smaller engines, such as used for outboard motors for boats, and where long periods of idle or fast idle operation are necessary.

In accordance with this invention, there has been provided in a system of the above type, a carburetor type fuel supply system for use in the low speed range where it is difficult for the mechanical fuel injection pump to meter accurately very small amounts of fuel. Use is made of the same Venturi control unit, the throttle body now acting as a carburetor as follows.

The idling or low load type of carburetor shown includes a float bowl 34 located at the underside of the throttle body which receives fuel via conduit 33 by gravity feed in the conventional manner from a fuel source, for example, tank 11. A float needle mechanism 35 maintains the fuel level in the bowl. A spray nozzle 36 leads from the small chamber 40 to the area behind the butterfly valve. An adjustable needle valve 37 regulates the amount of air passing into the chamber 40 which in turn determines the amount of fuel drawn into the mixing chamber from the bowl 34'via idle jet 39. Thus the manifold depression acting at jet 39 is modulated by allowing air to enter the system in controlled quantities through adjustment of the orifice formed by the needle valve 37 and its seat 38.

The amount of vacuum behind the valve 18 at which the idle fuel system becomes inoperative depends on the particular characteristics of the engine involved. Generally, the carburetor meters fuel in the low speed range and on an outboard motor for example, it would be operative in the idle and fast idle positions. In these positions the butterfly is near the closed position, and the vacuum formed behind the butterfly valve is relatively large and has caused the control rod to move to the right to the stop position. Under these circumstances, the throttle body is acting as a carburetor to meter fuel from the float bowl.

As the foot pedal is depressed in calling for additional speed, the valve 18 is opened more and the vacuum behind it decreases, that is to say, the absolute pressure increases. This causes the carburetor action to cease and simultaneously causes the diaphragm and control rod to move to the left, or the load position. By adjusting the various parts, such as injection pump diaphragm to cause the pump to deliver fuel at a predetermined value of the vacuum behind butterfly valve 18, the carburetor becomes operative when the pump becomes inoperative and viceversa.

Thus a common Venturi control unit has been provided for a combined injection-carburetor fuel supply system. The unit automatically causes the fuel injection pump or the carburetor to become operative when the other becomes inoperative.

Various modes of carrying out the invention are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.

I claim:

1. A combined injection and carburetor fuel supply system for an internal-combustion engine comprising, an injection fuel pump for delivering fuel to said engine, and a throttle control unit for supplying air to said engine, said unit including carburetor means operable in response to a vacuum in said unit greater than a first predetermined amount to supply fuel and air mixture to said engine at idle speed of the engine and control means for said pump to effect operation of said pump in response to a vacuum less than a second predetermined amount and control the delivery of said pump to said engine above the idle speed.

2. A combined injection and carburetor fuel supply system for an internal-combustion engine comprising, an injection fuel pump for delivering fuel to said engine, a diaphragm housing having a diaphragm therein for adjusting the delivery rate of said pump, a Venturi control unit for supplying air to said engine, said unit being in communication with said housing for moving said diaphragm whereby said pump delivers fuel to said engine at engine speeds other than idle, said unit also including carburetor means operated thereby for supplying fuel to said engine at idle speed of the engine.

3. A combined injection and carburetor fuel supply system for an internal-combustion engine comprising, an injection fuel pump for delivering fuel to said engine, a diaphragm unit for varying the delivery rate of said pump,

a Venturi throttle control unit for supplying air to said engine and for actuating said diaphragm unit whereby said pump delivers fuel to said engine at engine speeds other than idle, said throttle control unit including a fuel float bowl and idle system for supplying fuel to said engine when the vacuum in said control unit increases beyond a predetermined amount.

4. An injection fuel supply system for two-cycle internal-combustion engines of the type having a fuel pump for delivering fuel to the engine, a diaphragm unit for adjusting the pump delivery rate, and a throttle control unit for supplying air to the engine, said diaphragm unit connected with said control unit whereby said pump is adjusted in accordance with the vacuum in said control unit, the improvement residing in carburetion mechanism secured to said control unit and operated in response to a vacuum in said control unit greater than a first predetermined amount, said pump being operative in response to a vacuum in said control unit less than a second predetermined amount.

5. An injection fuel supply system for two-cycle internal-combustion engines of the type having a fuel pump for delivering fuel to the engine, a throttle control unit for supplying air to the engine, and a diaphragm housing including a diaphragm for adjusting the delivery of the fuel pump, said diaphragm housing connected with said control unit whereby said pump is adjusted in accordance with the vacuum in said control unit, the improvement residing in carburetion mechanism secured to said control unit and operated in response to a vacuum in said unit greater than a first predetermined amount, said pump being operative in response to a vacuum in said unit less than a second predetermined amount.

6. An injection fuel supply system for internal-combustion engines of the type having a fuel pump for delivering fuel to the engine, a throttle control unit for supplying air to the engine, and a diaphragm housing including a diaphragm for adjusting the delivery of the fuel pump, said diaphragm housing connected with said control unit whereby said pump is adjusted in accordance with the vacuum in said control unit, the improvement residing in a fuel float bowl and idle system secured to said control unit and operated in response to a vacuum in said unit greater thaua first predetermined amount, said pump being operative in response to a vacuum in said unit less than a second predetermined amount.

7. A throttle body for a combined injection and carburetor fuel supply system for an engine comprising, a mixing chamber for air and fuel and in communication with an engine intake, a throttle valve movably mounted in said chamber to control the intake of fuel and air mixture to the engine, said body adapted to receive a vacuum conduit which places said mixing chamber in communication with control means of a fuel injection pump, said throttle body also including carburetion means operative by a vacuum in said mixing chamber to supply fuel and air to said mixing chamber, said vacuum conduit being connected to said chamber at a location relative to said throttle valve effecting a stopping of the fuel injection pump when said throttle valve eflects supply of air and fuel from said carburetion means in response to a vacuum greater than a predetermined amount.

References Cited in the file of this patent UNITED STATES PATENTS 1,105,016 Bassford July 28, 1914 1,616,157 Werner Feb. 1, 1927 2,221,405 Nallinger Nev. 12, 1940 2,758,576 Schlamann Aug. 14, 1956 FOREIGN PATENTS 527,411 Great Britain May 21, 1940 975,937 France Mar. 12, 1951 

